CubeSat Camera CCAM : A Low Cost Imaging System for CubeSat Platforms William Brzozowski William Easdown
Contents What is CCAM? Design Drivers Uses for CCAM Detector Module Optics Module Optomechanics SNR challenges CCAM module
What is CCAM? UKATC and RAL Space collaboration - UKRI Modular Low cost Optics module and detector module 1.5U 5m GSD at 400km Earth orbital height = (2.58 arcsec) 2K x 2K detector 2⁰ field of view 1-2 year lifetime in Low Earth Orbit Optics module 150mm Detector module
CCAM Design Drivers Off-the-shelf components Compatibility with a 3 U CubeSat bus RGGB Bayer pattern off-the-shelf CMOS detector and FPGA FPU design Single aperture OT system mounted in the long axis of a 3U CubeSat Image quality NIIRS (National Image Interpretability Rating Scale) of level 2 [1] CCAM integrated into 3U cubesat structure
CCAM Uses CCAM is off the shelf Quicker and cheaper to launch Typical EO applications Interplanetary observations: geological activity, meteoroid environments, weather systems or landscape mapping Shandong Peninsula in Eastern China taken by Landsat 8 [2]
CCAM Detector Module 2048 x 2048 CMOS sensor FPGA for module control Memory included for buffering between FPU and OBC Uses regulated 3V3 and unregulated 6V lines from CubeSat All other voltages generated internally by low noise regulators No more than 2A will be drawn from a single line Overall power consumption around 6W CCAM detector module 2/3fps frame rate Blur minimised through 500µs exposures A selection of power modes allow easy enabling/disabling of components for maximum performance or power saving Utilises passive thermal control
CCAM Optics Module - Design
CCAM Optics Module - Performance Diffraction limited RMS spot size across visible and NIR wavelength range Pixel size for the CMOS sensor is 5.5μm RMS wavefront error is diffraction limited across full field of view = on axis field = off axis field = 400nm = 588nm = 900nm = diffraction limit = max off axis field = diffraction limit = 700nm
3-point kinematic mount connecting modules preserving optical alignment Can mount to numerous cubesat structures CCAM Optomechanics Optics module Detector module CMOS sensor Passive thermal compensation features: -20⁰C < T < +60⁰C M2 Vibration dampeners to mitigate various launch load vibration effects Field correcting lens M1 NIR filter
SNR Challenge SNR limited by: Cubesat volume i.e. aperture size CMOS sensor well capacity of 13500e - limits dynamic range Maximum possible exposure time ~500μs to avoid blur Shot and readout noise Dark current NIIRS level 2 achievable NIIRS level 2 reference image [3]
Possible solutions: - Image stacking - Longer exposure time SNR Challenge - Or using deployable apertures UKATC deployable cubesat: Current testing of UKATC deployable cubesat Folded state Deployed state
Summary Modular, low-cost imager for cubesat platforms Resilient to space and launch environments 3U or larger cubesats FPGA and CMOS sensor Diffraction limited reflective optics High resolution NIIRS level 2
Any Questions
References [1] https://fas.org/irp/imint/niirs.htm - accessed 22/05/18 [2] https://earthobservatory.nasa.gov/iotd/view.php?id=91195&src=ve - accessed 23/05/18 [3] https://fas.org/irp/imint/niirs_c/append.htm - accessed 24/05/18
Further details NIIRS level 2: Identify large (i.e., greater than 160 acre) centre-pivot irrigated fields during the growing season. Detect large buildings (e.g., hospitals, factories). Identify road patterns, like clover leafs, on major highway systems. Detect ice-breaker tracks. Detect the wake from a large (e.g., greater than 300') ship.